AbstractFourier transform carbon‐13 NMR spectra of a series of 3‐(X‐phenyl)glutaric anhydrides [X: H (2),4‐F (3), 4‐Cl (4), 4‐Br (5), 4‐OCH3(6), 4‐NO2(7), 3‐Cl (8) and 2,6‐Cl2(9)] and of 3‐methyl‐3‐(4‐chlorophenyl)‐ (10)‐, 3,3‐diphenyl‐ (11)‐ and 3,3‐(2,2′‐biphenylylene)‐glutaric anhydride (12) have been obtained and interpreted. Spectral assignments of the aromatic side‐chain carbons for3–9were made with the aid of additive parameters derived from suitably substituted toluenes for which unequivocal assignments are possible. The carbon‐13 and proton chemical shift data of the glutaric anhydride skeletal carbons and appended protons are compared and discussed in terms of conformational properties of the anhydride ring and its side‐chain. A set of substituent parameters (α: 17.6 ± 0.3 ppm, β: +7.0 ± 0.3 ppm and γ: −1.3 ± 0.3 ppm), which correlates the average effect of the XC6H4nucleus on the chemical shifts of the